The present invention relates to a process for electroless plating a metal on non-conductive materials, and more particularly, it relates to a process of depositing a metal layer on surfaces of various non-conductive materials such as plastics, glass, ceramic body, wood, stone, plaster body, cement article and articles made of bamboo etc. by electroless brushing or spraying chemical compositions onto said surface to bring about chemical reactions. This invention also relates to the products obtained by the above said process.
Processes for depositing metals on conductive materials by bath electroplating or by brush electroplating have been widely used for a long time. It is also well-known to deposit a metal on the surfaces of nonconductive material substrates by treating the surface to provide surface conductibility, and then depositing metals on the conductive surface of said non-conductive material by bath electroplating or brush electroplating (U.S. Pat. Nos. 4,481,081 and 4,165,394).
Surfaces of some non-conductive nonmetal materials such as ceramics, plastics etc. are first subjected to etching, then treated with a linking agent capable of providing sites for stannous ion adsorption on said surface by immersion or dipping, primed with aqueous solution containing stannous and copper ions by immersion or dipping, followed by immersion or dipping with a reducing agent capable of reducing the valence state of the copper ions, and finally electrolessly plated to deposit a metal layer on said surface. This process is also well known (U.S. Pat. No. 3,993,848).
However, up to now, all the existing processes for depositing metals on non-conductive material substrates cannot be carried out without a plating bath; that is to say, the substrate to be plated must be immersed or dipped in a pretreatment solution and plating solution. Therefore, the application of said processes is restricted by many factors. First, the dimensions of the substrate to be plated must be within a certain range since it is impossible to provide very large plating baths in practice. Then, the kinds of platable materials are restricted, since a porous material would absorb a large amount of plating solution resulting in greater expenses. Further, such processes are not suitable for plating only a portion of the surface of material.
Through investigation on the matter of electroless plating for years, the present inventor has found that metal can be deposited on the surfaces of various nonconductive material substrates only by brushing or spraying certain composite pretreatment solutions that are a sensitization solution and an activation solution, and a certain composite electroless plating solution, without the necessity of immersing said substrate in a bath solution.
The process according to the present invention does not require the immersing or dipping step existing in prior art processes, and it has the advantages of simplicity in apparatus and flexibility in process, by which a metal can be deposited on the surfaces of various nonconductive materials, either on the entire surfaces or on a portion of a surface, without any restriction of the dimensions and surface state of the substrate to be plated. Using the process of this invention, a metal can be deposited quickly and bound firmly on the surface of the substrate, with low consumption of pretreating and plating solutions. There is no restriction of the temperature at which the process is carried out. Further, no CN group is present in the composite solutions used in the present invention, and all the composite solutions are prepared from substances which are nontoxic and cause no pollution to the environment.